Ion channels alternate stochastically between two functional states, open and closed. This gating behavior is controlled by membrane potential or by the binding of neurotransmitters in voltage- and ligand-gated channels, respectively. Although much progress has been made in defining the structure and function of the ligand-binding cores and the voltage sensors, how these domains couple to channel opening remains poorly understood. Here we show that the M3 transmembrane segments of the NMDA receptor allosterically interact with both the ligand-binding cores and the channel gate. It is proposed that M3 functions as a transduction element whose conformational change couples ligand binding with channel opening. Furthermore, amino acid homology between glutamate receptor M3 segments and the equivalent S6 or TM2 segments in K(+) channels suggests that ion channel activation and gating are both structurally and functionally conserved.

Background: The alarming rise in the obesity epidemic and growing concern for the pathologic consequences of the metabolic syndrome warrant great need for development of obesity-related pharmacotherapeutics. The search for such therapeutics is severely limited by the slow throughput of animal models of obesity. Amenable to placement into a 96 well plate, zebrafish larvae have emerged as one of the highest throughput vertebrate model organisms for performing small molecule screens. A method for visually identifying non-toxic molecular effectors of fat metabolism using a live transparent vertebrate was developed. Given that increased levels of nicotinamide adenine dinucleotide (NAD) via deletion of CD38 have been shown to prevent high fat diet induced obesity in mice in a SIRT-1 dependent fashion we explored the possibility of directly applying NAD to zebrafish.

SUMMARY The hypothalamus integrates information required for the production of a variety of innate behaviors such as feeding, mating, aggression and predator avoidance. Despite an extensive knowledge of hypothalamic function, how embryonic genetic programs specify circuits that regulate these behaviors remains unknown. Here, we find that in the hypothalamus the developmentally regulated homeodomain-containing transcription factor Dbx1 is required for the generation of specific subclasses of neurons within the lateral hypothalamic area/zona incerta (LH) and the arcuate (Arc) nucleus. Consistent with this specific developmental role, Dbx1 hypothalamic-specific conditional-knockout mice display attenuated responses to predator odor and feeding stressors but do not display deficits in other innate behaviors such as mating or conspecific aggression. Thus, activity of a single developmentally regulated gene, Dbx1, is a shared requirement for the specification of hypothalamic nuclei governing a subset of innate behaviors.